Early January, usually one of our coldest winter months, has been uncharacteristically mild with daytime temperatures in the mid to upper 20s and lower 30s-degree Fahrenheit with about five inches of snow on the ground. These conditions create favorable fog conditions that form rime frost.
Rime frost, or rime ice, is formed when small supercooled water droplets of fog, mist, or cloud freeze on contact with a surface that is below freezing. The droplets are small, and they freeze almost instantly creating a mixture of beautiful, tiny accumulating ice crystals. The water droplets usually freeze on the windward side of tree branches, grasses, or other solid objects with a surface below freezing.
Another kind of frost, hoar frost, is often confused with rime frost, but here is the difference. Hoar frost is formed by direct deposition from water vapor to solid ice. A heavy coating of hoar frost looks similar to rime frost, but the formation process is much different. Hoar frost develops when there is no fog, but very high relative humidity above 90 percent and temperatures below 17 degrees Fahrenheit.
No matter how the frost develops, it surely beautifies our open landscapes turning them into a winter wonderland for all to enjoy.